Method for moving data extent

ABSTRACT

Disclosed is a computer program stored in a computer readable medium according to an exemplary embodiment of the present disclosure. The computer program performs the following method for moving an extent when being executed by one or more processors of a computing device and the method may include: deciding, by the processor, movement of an extent stored in a first disk in a disk space in which the disk space includes at least two disks; determining, by the processor, whether there is writing work for the extent based on extent mapping information for the extent; changing, by the processor, a state of the extent to read-only in the extent mapping information when there is no writing work for the extent; moving, by the processor, the extent positioned in the first disk to a second disk; and updating, by the processor, the extent mapping information based on completion of the disk movement of the extent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of Korean PatentApplication No. 10-2018-0069968 filed in the Korean IntellectualProperty Office on Jun. 19, 2018, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a database management method, and moreparticularly, to a method for moving data.

BACKGROUND ART

Businesses of enterprises are rapidly expanding with explosive datagrowth and the emergence of diverse environments and platforms. As newbusiness environments emerge, more efficient and flexible data servicesand information processing, and data management functions are needed. Inresponse to these changes, a research is continued on databases to solveproblems of high performance, high availability, and scalability whichare foundations of corporate business implementation.

A database management system (DBMS) can allow data files to be stored inrespective disks. In addition, the database management system can managea disk space including the disks. Thus, the database management systemcan enhance data integration and improve accessibility to data.Representative examples of the database management system includeTibero, Oracle, and IMS.

Korean Patent No. 10-0561229 discloses a duplicating apparatus in whicha plurality of original databases and a plurality of copy databases forma redundancy relationship. However, such a disclosure has a problem thatan input/output speed decreases due to a lot of processing operations,and a balance of a capacity between the databases is not matched.

Thus, there may be a demand in the art for a method for moving anextent, which minimizes a time for which work for the data isconstrained while maintaining consistency between the data in anoperation of moving the data.

SUMMARY OF THE DISCLOSURE

The present disclosure has been made in an effort to provide a methodfor moving an extent of a data file to another storage location.

An exemplary embodiment of the present disclosure provides a computerprogram stored in a computer readable medium. The computer programperforms the following method for moving an extent when being executedby one or more processors of a computing device and the method mayinclude: deciding, by the processor, movement of an extent stored in afirst disk in a disk space in which the disk space includes at least twodisks; determining, by the processor, whether there is writing work forthe extent based on extent mapping information for the extent; changing,by the processor, a state of the extent to read-only in the extentmapping information when there is no writing work for the extent;moving, by the processor, the extent positioned in the first disk to asecond disk; and updating, by the processor, the extent mappinginformation based on completion of the disk movement of the extent.

Alternatively, the extent mapping information may be configured for eachextent and may include at least one information of address informationof the extent, state information of the extent, and a transactionsequence number of the extent.

Alternatively, when the work for the extent occurs, the transactionsequence number of the extent may be updated to the transaction sequencenumber of a worker thread performing the work for the extent.

Alternatively, the determining of, by the processor, whether there isthe writing work for the extent based on the extent mapping informationfor the extent may include determining, by the processor, that there isthe writing work for the extent when there is the worker threadtransaction sequence number less than or equal to the transactionsequence number of the extent mapping information by comparing thetransaction sequence number of the extent mapping information and thetransaction sequence number of the worker thread and switching theworker thread performing the movement work for the extent to a sleepstate when there is the writing work for the extent.

Alternatively, the method may further include modifying, when thewriting work for the extent is completed, the transaction sequencenumber of the extent mapping information to the transaction sequencenumber of the worker thread.

Alternatively, the updating of by the processor, the extent mappinginformation based on the completion of the disk movement of the extentmay include determining, by the processor, whether there is the work forthe extent when the disk movement of the extent is completed andchanging an extent state of the extent mapping information to loadingwhen there is the work for the extent, updating the extent mappinginformation by waiting for the completion of the work, or updating theextent mapping information when there is no work for the extent.

Alternatively, when the extent state of the extent mapping informationis loading, the worker thread accessing the extent mapping informationmay be switched to a standby state and written in a standby list.

Alternatively, movement for the extent stored in the first disk may bedecided for rebalancing when a new disk is added to the disk space, theone or more disks are removed, or an error occurs in one of the at leasttwo disks.

Alternatively, the method may further include resuming, by theprocessor, the writing work for the extent based on the update of theextent mapping information.

Alternatively, the method may further include deleting, by theprocessor, the extent positioned in the first disk.

Another exemplary embodiment of the present disclosure provides a methodfor moving an extent, which is performed by one or more processors of acomputing device. The method may include: deciding, by the processor,movement of an extent stored in a first disk in a disk space in whichthe disk space includes at least two disks; determining, by theprocessor, whether there is writing work for the extent based on extentmapping information for the extent; changing, by the processor, a stateof the extent to read-only in the extent mapping information when thereis no writing work for the extent; moving, by the processor, the extentpositioned in the first disk to a second disk; and updating, by theprocessor, the extent mapping information based on completion of thedisk movement of the extent.

Yet another exemplary embodiment of the present disclosure provides acomputer device. The computing device may include: one or moreprocessors; and a memory storing commands executable in the one or moreprocessors, in which the one or more processors may decide movement ofan extent stored in a first disk in a disk space in which the disk spaceincludes at least two disks, determine whether there is writing work forthe extent based on extent mapping information for the extent, change astate of the extent to read-only in the extent mapping information whenthere is no writing work for the extent, move the extent positioned inthe first disk to a second disk, and update the extent mappinginformation based on completion of the disk movement of the extent.

According to an exemplary embodiment of the present disclosure, a methodfor moving an extent of a data file to another storage location can beprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a database system according to anexemplary embodiment of the present disclosure.

FIG. 2 is a conceptual view of a disk space according to an exemplaryembodiment of the present disclosure.

FIG. 3 is a full flow chart of a method for moving an extent accordingto an exemplary embodiment of the present disclosure.

FIG. 4 is a partial flow chart from reception of a movement command ofan extent up to completion of movement of the extent according to anexemplary embodiment of the present disclosure.

FIG. 5 is a partial flow chart from the completion of the movement ofthe extent up to resumption of writing work for the extent according toan exemplary embodiment of the present disclosure.

FIG. 6 is a flow chart illustrating a means for moving an extent in adatabase system according to an exemplary embodiment of the presentdisclosure.

FIG. 7 is a flow chart illustrating modules for moving an extent in adatabase system according to an exemplary embodiment of the presentdisclosure.

FIG. 8 is a flow chart illustrating logic for moving an extent in adatabase system according to an exemplary embodiment of the presentdisclosure.

FIG. 9 is a flow chart illustrating a circuit for moving an extent in adatabase system according to an exemplary embodiment of the presentdisclosure.

FIG. 10 is a block diagram of a computing device according to anexemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

Various embodiments will now be described with reference to drawings andlike reference numerals are used to refer to like elements throughoutall drawings. In the present specification, various descriptions arepresented to provide appreciation of the present disclosure. However, itis apparent that the embodiments can be executed without the specificdescription. In other examples, known structures and apparatuses arepresented in a block diagram form in order to facilitate description ofthe embodiments.

“Component”, “module”, “system”, and the like which are terms used inthe specification refer to a computer-related entity, hardware,firmware, software, and a combination of the software and the hardware,or execution of the software. For example, the component may be aprocessing process executed on a processor, the processor, an object, anexecution thread, a program, and/or a computer, but is not limitedthereto. For example, both an application executed in a computing deviceand the computing device may be the components. One or more componentsmay reside in the processor and/or the execution thread and onecomponent may be localized in one computer or distributed among two ormore computers. Further, the components may be executed by variouscomputer-readable media having various data structures, which are storedtherein. The components may perform communication through local and/orremote processing according to a signal (for example, data from onecomponent that interacts with other components and/or data throughanother system and a network such as the Internet through a signal in alocal system and a distribution system) having one or more data packets,for example.

The description of the presented exemplary embodiments is provided sothat those skilled in the art of the present disclosure use or implementthe present disclosure. Various modifications of the embodiments will beapparent to those skilled in the art and general principles definedherein can be applied to other embodiments without departing from thescope of the present disclosure. Therefore, the present disclosure isnot limited to the embodiments presented herein, but should be analyzedwithin the widest range which is consistent with the principles and newfeatures presented herein.

FIG. 1 is a schematic view of a database system according to anexemplary embodiment of the present disclosure.

As illustrated in FIG. 1, the database system 10 according to thepresent disclosure may include a client 200 and a database server 100.

As illustrated in FIG. 1, the client 200 may mean a node(s) in adatabase system having a mechanism for communication through a network.For example, the client 200 may include a predetermined electronicdevice having connectivity with a personal computer (PC), a laptopcomputer, a workstation, a terminal, and/or the network. Further, theclient 200 may include a predetermined server implemented by at leastone of agent, application programming interface (API), and plug-in. Forexample, the client 200 in FIG. 1 may be associated with a user (e.g.,database administration (DBA)) using the database server 100.

The database server 100 may include a predetermined type of computersystem or computing device such as a microprocessor, a mainframecomputer, a digital single processor, a portable device, and a devicecontroller. Each of the database servers 100 may include a databasemanagement system (DBMS) 110 and a persistent storage 130. In addition,the database server 100 may be used interchangeably with a device forexecuting a query.

In FIG. 1, only one database server 100 is illustrated, but it will beapparent to those skilled in the art that database servers there thanmay also be included in the scope of the present disclosure and thedatabase server 100 may include additional components. That is, thedatabase server 100 may be constituted by a plurality of computingdevices. A set of a plurality of nodes may constitute the databaseserver 100. For example, although not illustrated in FIG. 1, thedatabase server 100 may include one or more memories 120 including abuffer cache. Further, although not illustrated in FIG. 1, the databaseserver 100 may include one or more processors 111. Therefore, the DBMS110 may be operated by the processor 111 on the memory 120.

The memory 120 in the present specification as a primary storage devicedirectly accessed by the processor, such as a random access memory (RAM)including a dynamic random access memory (DRAM), a static random accessmemory (SRAM), etc., may mean a volatile storage device in which storedinformation is momentarily erased when power is turned off, but is notlimited thereto. The memory 120 may be operated by the processor 111.The memory 120 may temporarily store a data table including a datavalue. The data table may include the data value and in the exemplaryembodiment of the present disclosure, the data value of the data tablemay be written in the persistent storage 130 from the memory 120. In anadditional aspect, the memory 120 may include the buffer cache and datamay be stored in a data block of the buffer cache. The data stored inthe buffer cache may be written in the persistent storage by abackground process.

The persistent storage 130 may mean a non-volatile storage medium whichmay consistently store predetermined data, such as a magnetic disk, anoptical disk, and a magneto-optical storage device and a storage devicebased on a flash memory and/or a battery-backup memory. The persistentstorage 130 may communicate with the processor and the memory of thedatabase server 100 through various communication means. In anadditional exemplary embodiment, the persistent storage 130 ispositioned outside the database server 100 to communicate with thedatabase server 100.

The DBMS 110 as a program for permitting the database server 100 toperform operations including parsing of a query, retrieval, insertion,modification, and/or deletion of required data may be implemented by theprocessor 111 in the memory 120 of the database server 100 as describedabove.

The client 200 and the database server 100 or the database servers mayalso communicate with each other through the network (not illustrated).The network according to the exemplary embodiment of the presentdisclosure may use various wired communication systems such as publicswitched telephone network (PSTN), x digital subscriber line (xDSL),rate adaptive DSL (RADSL), multi rate DSL (MDSL), very high speed DSL(VDSL), universal asymmetric DSL (UADSL), high bit rate DSL (HDSL), andlocal area network (LAN).

The network presented in the present specification may use variouswireless communication systems such as code division multi access(CDMA), time division multi access (TDMA), frequency division multiaccess (FDMA), orthogonal frequency division multi access (OFDMA),single carrier-FDMA (SC-FDMA), and other systems. For example, thenetwork may include a database link (dblink), and as a result, aplurality of database servers communicates with each other through thedatabase link to fetch data from another database server 100. Thetechniques described in the present specification may be used in othernetworks in addition to the aforementioned networks.

FIG. 2 is a conceptual view of a disk space 300 according to anexemplary embodiment of the present disclosure.

The database server 100 may include the disk space 300 capable ofstoring data and the processor 111. Herein, the disk space may store anencrypted signal, a database table, or a data stream that is a stream ofthe data, which is transmitted to the database server 100 via thenetwork. Further, the disk space 300 may include one or more disks 310and 330 that may store data files. Further, the processor 111 may decideto separate the received data stream into the unit of the extent andstore the data stream in one of one or more disks.

In the following text, extent as a series of data units having a size of0 bit or more may denote a basic unit for storing data. For example, theextent may be configured as a size of 1 Mb, but the present disclosureis not limited thereto. The extent may include an original extentlocated in a first disk 310 before movement and a copy extent stored ona second disk 330 after movement.

The processor 111 may divide the data stream into extent units andallocate the data streams to one or more disks 310 and 330. Here, theone or more disks 310 and 330 may be at least one of disks included inthe disk space 300. For example, when the processor 111 receives a datastream of “A, A′, B, B′, and C and C′” over the network, the processor111 may divide the data stream into 6 of “A 311”, “A′ 331”, “B 312”, “B′332”, C 313, and C′ 333 into 6 extents. Herein, each extent may have thesize of 1 Mb. In addition, as illustrated in FIG. 2, the processor mayallocate “A 311”, “B 312”, and “C 313” to the first disk 310 and “A′331”, “B′ 332”, and “C′ 333” to the second disk 330. As a result, theprocessor 111 may divide the data stream and separately store thedivided data streams in one or more disks 310 and 330. The detaileddescription of allocation and storage operations of the above-describedextents is only an example, and the present disclosure is not limitedthereto.

The memory 120 according to an exemplary embodiment of the presentdisclosure may store extent mapping information related to a locationwhere each extent is stored. In another exemplary embodiment of thepresent disclosure, one of nodes constituting the database server maystore the extent mapping information including information regarding anode where each extent is stored. More specifically, the processor 111may store the extent mapping information for the location (e.g., a disknumber and a storage location) where each extent is stored in aninstance cache of the DB or on the memory 120. In addition, a workerthread of the processor 111 may access the extent based on the extentmapping information in order to perform work related to the extent.

Additionally, the database server 100 may include at least two or morenodes (computing devices) (not illustrated). The node may include a DBMSnode and a storage manager node. Herein, the storage manager may be aseparate node capable of generating or transmitting a command related tothe operation of the DBMS 110. That is, the storage manager may be anode separated from the DBMS or it may be another instance whichoperates on the same computing device as the DBMS. More specifically,the database server 100 may include one or more processors 111. Inaddition, the DBMS 110 and the storage manager may be separate instancesoperated by processors different from each other, respectively. Further,herein, when the DBMS 110 manages the persistent storage medium 130, thestorage manager may transmit a command (e.g., a move command for theextent) to control the DBMS to perform a predetermined operation to theDBMS 110. In addition, the storage manager may store and manage theextent mapping information in a separate buffer cache. Further, in someexemplary embodiments, the storage manager may be included in thedatabase system 10 and configured to communicate with the databaseserver 100 over the network as a computing device different from thedatabase server 100.

The extent mapping information according to an exemplary embodiment ofthe present disclosure may include at least one of address informationof the extent, state information of the extent, and a transactionsequence number of the extent. Here, the address information of theextent may include information for accessing the extent, such as thedisk number and the storage location of the extent. In addition, theextent state information may be configured to indicate whether theextent is being performed (e.g., loading or loaded) or indicate whetherthe extent is accessible (e.g., read-only, read/write available, etc.).In addition, the transaction sequence number of the extent may be apredetermined time stamp, which is decided based on an occurrence timeof the transaction for each extent. For example, the transactionsequence number may consist of eight hexadecimal digits and may bestored on the extent mapping information for each extent. Thedescription of the configuration of the transaction sequence number isjust an example and the present disclosure is not limited thereto. Thedetailed description of the extent mapping information is only anexample, and the present disclosure is not limited thereto.

The transaction sequence number of the extent on the extent mappinginformation according to an exemplary embodiment of the presentdisclosure may be updated to a transaction sequence number of the workerthread performing the work related to the extent when the work relatedto the extent occurs.

More specifically, the processor 111 may manage the extent mappinginformation for each extent and the worker thread performing the workrelated to the extent. Then, the processor 111 may store the transactionsequence number decided based on an access time in items (one variableitem in a header of the worker thread) included in the worker threadwhen the worker thread accesses a predetermined extent in order toperform the work. Further, when the work related to the extent occurs,the processor 111 may update the transaction sequence number of theextent to the transaction sequence number of the worker threadperforming the work related to the extent. Accordingly, the processor111 may store the transaction sequence number decided based on the timewhen the worker thread accesses the extent in the extent mappinginformation for the extent.

Accordingly, the processor 111 according to an exemplary embodiment ofthe present disclosure may determine whether there is writing work forthe extent based on the extent mapping information. The detaileddescription thereof will be described below with reference to FIGS. 3and 4.

FIG. 3 is a full flow chart of a method for moving an extent accordingto an exemplary embodiment of the present disclosure.

The extent movement according to an exemplary embodiment of the presentdisclosure may be performed by a computing device. Herein, the computingdevice may include one or more processors 111 and a memory storingcommands executable by one or more processors. Hereinafter, an order inwhich the computing device moves the extents will be described indetail.

The computing device according to an exemplary embodiment of the presentdisclosure may decide movement of the extent stored in the first disk310 in the disk space (401). Herein, the movement command for the extentmay be received from an external client 200 or may be autonomouslygenerated by the process of the DBMS when the process of the DBMSdetermines that the movement of the extent is required. In addition,according to another exemplary embodiment of the present disclosure, amove request for the extent may be received from the storage managernode that is different from the computing device.

More specifically, when a new disk is added to the disk space 300, oneor more disks are removed, or an error occurs in one of at least twodisks, the computing device may decide to move the extent stored in thefirst disk 310 to the second disk 330 for rebalancing. Herein, the diskspace may include at least two disks 310 and 330. In addition, inanother exemplary embodiment of the present disclosure, the databaseserver may include the storage manager node when the database server isconstituted by a plurality of nodes. Further, in another exemplaryembodiment of the present disclosure, the disk space may include disksof different nodes, or may include a plurality of disks in one node.

More specifically, as a third disk (not illustrated) is added to thedisk space 300, the computing device may decide to move some of extents211, 212, 213, 231, 232, and 233 stored in the first and second disks310 and 330 to the third disk (not illustrated). Accordingly, thecomputing device may perform the rebalancing between the disks byreallocating the extents between the disks. Here, the extentreallocation may be performed based on, for example, a capacity of eachdisk.

For example, the third disk (not illustrated) having a capacity of 10 Mbmay be added to the disk space including the first disk 310 and thesecond disk 330 each having the capacity of 10 Mb. In this case, thecomputing device may decide to move “C 313” among the extents “A 311”,“B 312”, and “C 313” stored in the first disk 310 to the third disk (notillustrated) and move the extent “C′ 333” stored in the second disk 330to the third disk (not illustrated). The detailed description of theextent movement operation is only an example, and the present disclosureis not limited thereto.

The computing device according to an exemplary embodiment of the presentdisclosure may determine whether there is writing work for the extentbased on the extent mapping information for the extent (402). Herein, anentry included in the extent mapping information may store thetransaction sequence number decided based on a time at which the workperformed for each extent starts.

More specifically, the computing device may separate the data streamsinto the extent units and allocate the separated data streams to one ormore disks included in the disk space. In addition, the computing devicemay store the extent mapping information for each of the extents in acache memory or in a main memory. Here, the extent mapping informationmay include at least one of the address information of the extent, thestate information of the extent, and the transaction sequence number ofthe extent. Here, the transaction sequence number as a type of timestamp that increases in a time series may be changed over time.

The computing device may include the worker thread that performs thework related to the extent. Further, the computing device may store thetransaction sequence number decided based on the access time in theitems (e.g., one variable item in the header of the worker thread)included in the worker thread when the worker thread accesses apredetermined extent in order to perform the work. In addition, when thework related to the extent occurs, the computing device may update thetransaction sequence number of the extent to the transaction sequencenumber of the worker thread performing the work related to the extent.Accordingly, the computing device may store the transaction sequencenumber decided based on the time when the worker thread accesses theextent in the entry of the extent mapping information for the extent.

As a result, the computing device may compare the transaction sequencenumber stored in the entry of the extent mapping information and thetransaction sequence number stored in the worker thread being driven,respectively. In addition, according to whether there is the workerthread with the transaction sequence number which is small than or equalto the transaction sequence number of the extent mapping information,the computing device may determine that the work (e.g., writing work forthe extent) for the extent is not present.

When the computing device according to an exemplary embodiment of thepresent disclosure determines that there is the work for the extent, thecomputing device may decide to switch the worker thread performing themovement work for the extent to the sleep state.

More specifically, the computing device may determine that there is thework for the extent when there is a worker thread with a transactionsequence number which is small than or equal to the transaction sequencenumber of the extent mapping information. In addition, the computingdevice may decide to switch the worker thread accessing to move theextent to a sleep state. Herein, the sleep state indicates waiting forthe movement work of the extent and the computing device may decide toallow the worker thread to access the extent again after a predeterminedtime. Accordingly, the computing device may make the worker threadperforming the movement work of the extent wait until the worker threadperforming the writing work for the extent completes the writing work.The computing device determines the presence or absence of the work ofthe worker thread for the extent before the movement work of the extentand when the work for the extent is not present, the computing deviceperform the movement work to maintain consistency of the transaction.

When the writing work for the extent is not present, the computingdevice according to an exemplary embodiment of the present disclosuremay change a state of the extent to read-only in the extent mappinginformation (403).

More specifically, the computing device compares the transactionsequence number of the extent mapping information and the transactionsequence number of the worker thread to determine whether the writingwork for the extent is present. In addition, when there is no workerthread with the transaction sequence number which is small than or equalto the transaction sequence number of the extent mapping information,the computing device may determine that the writing work for the extentis not present. Further, the computing device may change the stateinformation of the extents included in the extent mapping information toread-only. Herein, a read-only state which locks the writing work forthe extent may allow the access of the worker thread for performingreading work.

The computing device according to an exemplary embodiment of the presentdisclosure may move the extent positioned in the first disk 310 to thesecond disk 330 (404). More specifically, the computing device may readand copy the original extent positioned in the first disk 310. Inaddition, the computing device may store the copy extent copied from theoriginal extent in the second disk 330. Additionally, after the movementof the extent is completed and modification of the extent mappinginformation is completed, the computing device may delete the originalextent positioned in the first disk 310. By deleting a pre-movementextent after the modification of the extent mapping information as wellas the extent migration is completed, the method for moving an extentaccording to an embodiment of the present disclosure may efficientlymanage the storage space of the computing device while maintaining theconsistency.

When the writing work for the extent is completed, the computing devicemay modify the transaction sequence number of the extent mappinginformation to the transaction sequence number of the worker thread.More specifically, the computing device may initialize the transactionsequence number of the worker thread when the writing work of the workerthread for the extent is completed. Herein, the initialization of thetransaction sequence number may be a change to the transaction sequencenumber at the time of completion of the work. Additionally, theinitialization of the transaction sequence number may mean a change to apredetermined value (e.g., “FFFFFFFF” in hexadecimal 8-digit number).The predetermined value is just an example and the present disclosure isnot limited thereto.

The computing device according to an exemplary embodiment of the presentdisclosure may update the extent mapping information based on completionof disk movement of the extent (405). In addition, in some exemplaryembodiments, when the disk movement of the extent is completed, thecomputing device may determine whether there is the work for the extent.Further, when there is the work for the extent, the computing device maychange the extent state of the extent mapping information to an in-usestate and update the extent mapping information by waiting for thecompletion of the work or update the extent mapping information whenthere is no work for the extent, (405).

More specifically, the computing device may store on a cache the entryof the extent mapping information for each extent. Herein, the extentmapping information may include at least one of the address information(e.g., disk number, etc.) of the extent, the state information of theextent, and the transaction sequence number of the extent. Further, thetransaction sequence number as a type of time stamp that increases in atime series may be changed over time. The computing device may thenstore the transaction sequence number decided based on the access timein the items included in the worker thread accessing for the movementwork for the extent. In addition, when the movement work for the extentoccurs, the computing device may update the transaction sequence numberof the extent to the transaction sequence number of the worker threadperforming the movement work for the extent. Accordingly, the computingdevice may store the transaction sequence number decided based on thetime when the worker thread accesses the extent in the entry of theextent mapping information for the extent.

The computing device may compare the transaction sequence number storedin the entry of the extent mapping information and the transactionsequence number stored in the worker thread being driven, respectively.In addition, according to whether there is the worker thread with thetransaction sequence number which is small than or equal to thetransaction sequence number of the extent mapping information, thecomputing device may determine whether the work (e.g., reading orwriting work for the extent) for the extent is present. Morespecifically, the computing device may determine that there is the workfor the extent when there is a worker thread with a transaction sequencenumber which is small than or equal to the transaction sequence numberof the extent mapping information. On the contrary, the computing devicemay determine that there is no work for the extent when there is noworker thread with a transaction sequence number which is small than orequal to the transaction sequence number of the extent mappinginformation.

The computing device may change the extent state included in the extentmapping information to loading when there is the work for the extent. Inaddition, the computing device may change the extent state to loadedwhen there is no work on the extent or after the completion of the work.The computing device may then wait for an update to the extent mappinginformation until the extent state is changed to loaded. In an exemplaryembodiment of the present disclosure, when there is the work (e.g., areading work, etc.) for the extent, in a situation where the extent isstored in an existing storage location and a moved storage location, bywaiting for the update of the extent mapping information includinginformation for accessing the extent, the work for the extent may beperformed on the extent stored in the existing storage location, therebyminimizing downtime due to the movement of the extents.

When the extent state of the extent mapping information is loading, thecomputing device according to an exemplary embodiment of the presentdisclosure may switch the worker thread accessing the extent mappinginformation to a standby state and write the worker thread in a standbylist. More specifically, the computing device may decide to allow theaccess of the worker thread based on the extent state included in theextent mapping information. Herein, the extent state may be loading orloaded and may be configured in a form of read-only or read/writeavailable for indicating whether the extent is accessible.

The computing device may decide to suspend the operation of the workerthread when the worker thread accesses the extent in which the extentstate is loading. In addition, the computing device may create thestandby list on the cache and stack one or more worker threads of whichoperations are suspended in order. Herein, the standby list may becreated for each extent, created for each disk, or created as onestandby list for the entire disk space. Further, the computing devicemay reconfirm the extent state after a predetermined time and decide toresume the operation of the worker thread when the extent state isloaded.

As a result, the method for moving an extent according to an exemplaryembodiment of the present disclosure may minimize a time for which aread request is blocked in an operation of moving the extent. Further,by comparing only the transaction sequence numbers of the entry and theworker thread, it is possible to determine whether the extent is worked,thereby reducing a memory usage.

Then, since the extent movement work is performed by judging whether thewriting work is being performed for each extent, the consistency of datamay be maintained. Further, when I/O work for the extent is beingperformed, it is possible to wait for the update of the extent mappinginformation, thereby preventing duplication and the error of data.

The method for moving an extent according to an exemplary embodiment ofthe present disclosure performs work of replicating the extent toanother storage location while allowing the reading work for the extent,thereby minimizing the time for which the reading work for the extent isblocked. In addition, the method for moving an extent according to anexemplary embodiment of the present disclosure checks the existence ofthe reading work for the extent and updates the extent mappinginformation indicating the storage location of the extent only whenthere is no work, thereby maintaining the consistency. That is, themethod for moving an extent according to an exemplary embodiment of thepresent disclosure may maintain the consistency while minimizing thetime for which the reading and writing work for the extent is blocked,thereby enhancing performance of a database computer device.

FIG. 4 is a partial flow chart from reception of a movement command ofextent up to completion of movement of the extent according to anexemplary embodiment of the present disclosure.

The computing device according to an exemplary embodiment of the presentdisclosure may decide movement of the extent stored in the first disk(501). Herein, the movement of the extent may be decided for rebalancingwhen a new disk is added to the disk space 300, one or more disks areremoved, or the error occurs on one of at least two disks. Thedescription of a situation in which the movement of the extent isdecided is just an example and the present disclosure is not limitedthereto.

More specifically, when a new disk is added to disk space 300, one ormore disks are removed, or an error occurs in one of at least two disks,the computing device may decide to move the extent stored in the firstdisk 310 to the second disk 330 for rebalancing. Herein, the disk spacemay include at least two disks 310 and 330. Further, in some exemplaryembodiments, the computing device may include the DBMS processor and thestorage manager node. In addition, the storage manager node may transmita command related to the extent movement to the DBMS processor.

The extent mapping information according to an exemplary embodiment ofthe present disclosure may include at least one of address informationof the extent, state information of the extent, and a transactionsequence number of the extent. In addition, the extent mappinginformation may be configured for each extent and stored in at least oneof the cache, the memory, and an external storage manager.

Herein, the address information of the extent may include informationfor accessing the extent, such as the disk number and the storagelocation of the extent. In addition, the extent state information may beconfigured to indicate whether the work for the extent is beingperformed (e.g., loading or loaded) or indicate whether the extent isaccessible (e.g., read-only, read/write available, etc.). In addition,the transaction sequence number of the extent may be a predeterminedformat of time stamp, which is decided based on an occurrence time ofthe transaction for each extent.

According to an exemplary embodiment of the present disclosure, thetransaction sequence number of the extent may be configured for eachextent and stored in the entry on the extent mapping information.Further, the computing device may store the transaction sequence numberin the worker thread when the worker thread accesses the extent for thework. In addition, when the work related to the extent occurs, thetransaction sequence number of the extent may be updated to thetransaction sequence number of the worker thread performing the workrelated to the extent. Accordingly, each entry on the extent mappinginformation may store the transaction sequence number of the workerthread accessing to perform the work for the extent. The processorcompares the transaction sequence number of the extent mappinginformation and the transaction sequence number of the worker threadthrough the update of the transaction sequence number to determinewhether the work for the extent is present.

The computing device may confirm the transaction sequence number storedin each of the worker threads. Herein, the computing device maydetermine whether there is the transaction sequence number of the workerthread is smaller than or equal to the transaction sequence number ofthe extent mapping information (502).

First, the computing device may determine that there is the work for theextent when there is the transaction sequence number of the workerthread is smaller than or equal to the transaction sequence number ofthe extent mapping information (503).

In such a case, the computing device may switch the worker thread (i.e.,the worker thread performing the extent movement work) accessing formoving the extent to a sleep state (504). Herein, the sleep stateindicates waiting for the movement of the extent and the computingdevice may decide to allow the worker thread to access the extent againafter a predetermined time. Accordingly, the computing device may makethe worker thread performing the movement work of the extent to waituntil the worker thread performing the writing work for the extentcompletes the writing work.

When the writing work for the extent is completed, the computing devicemay modify the transaction sequence number of the extent mappinginformation to the transaction sequence number of the worker thread(i.e., a worker thread performing the writing work for the extent)(505).

More specifically, the computing device may initialize the transactionsequence number of the worker thread when the writing work of the workerthread for the extent is completed. Herein, the initialization of thetransaction sequence number may be a change to the transaction sequencenumber at the time of completion of the work. Additionally, theinitialization of the transaction sequence number may mean a change to apredetermined value (e.g., “FFFFFFFF” in hexadecimal 8-digit number).

First, the computing device may determine that the writing work for theextent is completed when there is no transaction sequence number of theworker thread less than or equal to the transaction sequence number ofthe extent mapping information (506).

In such a case, the computing device may change the state information ofthe extents included in the extent mapping information to read-only(507). Herein, a read-only state which locks the writing work for theextent may allow the access of the worker thread for performing readingwork.

The computing device may switch the worker thread performing themovement work of the extent that is in the sleep state to an awake state(508). Herein, the awake state means a state in which the movement workfor the extent is performed or may be performed and the computing devicemay resume the movement work of the worker thread.

The computing device may allow the worker thread performing the extentmovement work to move the extent position in the first disk 310 to thesecond disk 330 (509). More specifically, the computing device may allowthe worker thread corresponding to the extent movement work to copy theoriginal extent in the first disk 310. In addition, the computing devicemay allow the worker thread to store the copy extent copied from theoriginal extent in the second disk 330. Additionally, the computingdevice may allow the worker thread to delete the original extentpositioned in the first disk 310 after the copy extent is stored in thesecond disk 330.

For example, the extents “A 311”, “B 312”, and “C 313” may be stored inthe first disk 310 as illustrated in FIG. 2. In addition, the computingdevice may receive a command for moving the extents “A 311”, “B 312”,and “C 313” to the second disk 330. Accordingly, the computing devicemay confirm the transaction sequence number constituted by thehexadecimal 8-digit number of the extent mapping informationcorresponding to “A 311”, “B 312”, and “C 313” and compare thetransaction sequence number of the worker thread which is in operationwith the configured transaction sequence number. Herein, the transactionsequence number for “A 311” may be “2018AA99”, the transaction sequencenumber for “B 312” may be “2018AB00”, and the transaction sequencenumber for “C 313” may be “2018DD80”. In addition, one worker threadhaving the smallest transaction sequence number among the worker threadswhich are in operation may include a transaction sequence number“2018AB12”. Accordingly, the computing device may determine that thereis writing work corresponding to the extent “C 313” and determine thatthere is no writing work corresponding to “A 311” and “B 312”. Inaddition, the computing device may cause the worker thread for theextent movement work to perform the movement work for the extents “A311” and “B 312”. Further, the computing device may switch the workerthread for the movement work for the extent “C 313” to the sleep state.Then, the computing device may allow the worker thread to attempt toaccess the extent “C 313” at an interval of 1/100 second to confirm theend of the movement work. Further, the computing device may switch theworker thread in the sleep state to the awake state when the writingwork for “C 313” is completed. As a result, the computing device maymove the extents “A 311”, “B 312”, and “C 313” positioned in the firstdisk 310 to the second disk 330 and store the extents as “A′ 331”, “B′332”, and “C′ 333”. The detailed description of a determinationoperation of the existence of the writing work for the extent and themovement work of the worker thread is just an example and the presentdisclosure is not limited thereto.

Accordingly, in the method for moving an extent according to anexemplary embodiment of the present disclosure, in the operation ofmoving the extent, since the extent movement work is performed bydetermining whether the writing work is performed for each extent, theconsistency of the data may be maintained.

By changing the state of the extent included in the extent mappinginformation to read-only, it is possible to minimize the time for whichthe read request is blocked. Further, by comparing only the transactionsequence numbers of the entry and the worker thread, it is possible todetermine whether the extent is worked, thereby reducing a memory usage.

FIG. 5 is a partial flow chart from the completion of the movement ofthe extent up to resumption of writing work for the extent according toan exemplary embodiment of the present disclosure.

The computing device according to an exemplary embodiment of the presentdisclosure may update the extent mapping information based on completionof disk movement of the extent (510). More specifically, when the diskmovement of the extent is completed, the computing device may determinewhether there is the work for the extent. In addition, when there is thework for the extent, the computing device may change the extent state ofthe extent mapping information to the in-use state and update the extentmapping information by waiting for completion of the work. On thecontrary, when there is no work for the extent, the computing device mayupdate the extent mapping information (514).

Herein, the operation of the computing device of determining whetherthere is the work for the extent may be performed by comparing thestored transaction sequence number of the extent mapping informationwith the transaction sequence number stored in the worker thread asdescribed above with reference to FIG. 4. More specifically, thecomputing device may store on a cache the entry of the extent mappinginformation for each extent. Herein, the extent mapping information mayinclude at least one of the address information (e.g., disk number,etc.) of the extent, the state information of the extent, and thetransaction sequence number of the extent. Further, the transactionsequence number as a type of time stamp that increases in a time seriesmay be changed over time. The computing device may then store thetransaction sequence number decided based on the access time in theitems included in the worker thread accessing for the movement work forthe extent. In addition, when the movement work for the extent occurs,the computing device may update the transaction sequence number of theextent to the transaction sequence number of the worker threadperforming the movement work for the extent. Accordingly, the computingdevice may store the transaction sequence number decided based on thetime when the worker thread accesses the extent in the entry of theextent mapping information for the extent.

The computing device may compare the transaction sequence number storedin the entry of the extent mapping information and the transactionsequence number stored in the worker thread being driven, respectively.In addition, according to whether there is the worker thread with thetransaction sequence number which is small than or equal to thetransaction sequence number of the extent mapping information, thecomputing device may determine whether the work (e.g., reading orwriting work for the extent) for the extent is present (511). Morespecifically, the computing device may determine that there is the workfor the extent when there is a worker thread with a transaction sequencenumber which is small than or equal to the transaction sequence numberof the extent mapping information. On the contrary, the computing devicemay determine that there is no work for the extent when there is noworker thread with a transaction sequence number which is small than orequal to the transaction sequence number of the extent mappinginformation.

The computing device may change the extent state included in the extentmapping information to loading when there is the work for the extent(512). In addition, the computing device may change the extent state toloaded when there is no work on the extent or after the completion ofthe work. The computing device may then wait for an update to the extentmapping information until the extent state is changed to loaded.

When the extent state of the extent mapping information is loading, thecomputing device according to an exemplary embodiment of the presentdisclosure may switch the worker thread accessing the extent mappinginformation to a standby state and write the worker thread in a standbylist (513). More specifically, the computing device may decide to allowthe access of the worker thread based on the extent state included inthe extent mapping information. Herein, the extent state may be loadingor loaded for indicating whether the work for the extent is performed.The extent state may be configured in a form of read-only or read/writeavailable for indicating whether to be accessible to the extent.

The computing device may decide to suspend the operation of the workerthread when the worker thread accesses the extent in which the extentstate is loading. In addition, the computing device may create thestandby list on the cache and stack one or more worker threads of whichoperations are suspended in order. Herein, the standby list may becreated for each extent, created for each disk, or created as onestandby list for the entire disk space 300. Further, the computingdevice may reconfirm the extent state after a predetermined time anddecide to resume the operation of the worker thread the extent state isloaded.

Additionally, the computing device may store the transaction sequencenumber decided based on the access time in the worker thread accessingthe extent of which extent state is loading. In addition, the computingdevice may decide the order of the standby list by comparing the sizesof the transaction sequence numbers stored in the respective workerthreads. For example, when a first worker thread and a second workerthread access the extent of which extent state is loading, the firstworker thread stores a transaction sequence number “201812FF” in aheader thereof and the second worker thread may store a transactionsequence number “201870AB” in the header thereof based on respectiveaccess time. In addition, the operations of the first worker thread andthe second worker thread are held by the computing device and stored inthe standby list on the cache. In this case, the computing devicecompares the transaction sequence number “201812FF” of the first workerthread and the transaction sequence number “201870AB” of the secondworker thread to decide to process the first worker thread storing thesmaller transaction sequence number in a higher priority than the secondworker thread. The detailed description of the values of the transactionsequence numbers and the standby list is only an example and the presentdisclosure is not limited thereto.

As a result, the method for moving an extent according to an exemplaryembodiment of the present disclosure may minimize a time for which a redrequest is blocked in an operation of moving the extent. Further, bycomparing only the transaction sequence numbers of the entry and theworker thread, it is possible to determine whether the extent is worked,thereby reducing a memory usage.

Then, since the extent movement work is performed by judging whether thewriting work is being performed for each extent, the consistency of datamay be maintained. Further, when I/O work for the extent is beingperformed, it is possible to wait for the update of the extent mappinginformation, thereby preventing duplication and the error of data.

FIG. 6 is a flow chart illustrating a means for moving an extent in adatabase system 10 according to an exemplary embodiment of the presentdisclosure.

A means for moving an extent may include a means 601 for deciding, oneor more processors of a computing device, movement of an extent storedin a first disk in a disk space in which the disk space includes atleast two disks; a means 602 for determining, by the processor, whetherthere is writing work for the extent based on extent mapping informationfor the extent, a means 603 for changing, by the processor, a state ofthe extent to read-only in the extent mapping information when there isno writing work for the extent, a means 604 for moving, by theprocessor, the extent positioned in the first disk to a second disk, anda means 605 for updating, by the processor, the extent mappinginformation based on completion of the disk movement of the extent.

Alternatively, the extent mapping information may be configured for eachextent and may include at least one information of address informationof the extent, state information of the extent, and a transactionsequence number of the extent.

Alternatively, when the work for the extent occurs, the transactionsequence number of the extent may be updated to the transaction sequencenumber of a worker thread performing the work for the extent.

Alternatively, the means for determining, by the processor, whetherthere is the writing work for the extent based on the extent mappinginformation for the extent may include a means for determining, by theprocessor, that there is the writing work for the extent when there isthe worker thread transaction sequence number less than or equal to thetransaction sequence number of the extent mapping information bycomparing the transaction sequence number of the extent mappinginformation and the transaction sequence number of the worker thread anda means for switching the worker thread performing the movement work forthe extent to a sleep state when there is the writing work for theextent.

Alternatively, the means may further include a means for modifying, whenthe writing work for the extent is completed, the transaction sequencenumber of the extent mapping information to the transaction sequencenumber of the worker thread.

Alternatively, the means for updating, by the processor, the extentmapping information based on the completion of the disk movement of theextent may include a means for determining, by the processor, whetherthere is the work for the extent when the disk movement of the extent iscompleted and a means for changing an extent state of the extent mappinginformation to loading when there is the work for the extent, updatingthe extent mapping information by waiting for the completion of thework, or updating the extent mapping information when there is no workfor the extent.

Alternatively, when the extent state of the extent mapping informationis loading, the worker thread accessing the extent mapping informationmay be switched to a standby state and written in a standby list.

Alternatively, a movement command for the extent stored in the firstdisk may be created for rebalancing when a new disk is added to the diskspace, the one or more disks are removed, or an error occurs in one ofthe at least two disks.

Alternatively, the means may further include a means for resuming, bythe processor, the writing work for the extent based on the update ofthe extent mapping information.

Alternatively, the means may further include a means for deleting, bythe processor, the extent positioned in the first disk.

FIG. 7 is a flow chart illustrating a module for moving an extent in adatabase system 10 according to an exemplary embodiment of the presentdisclosure.

The method for moving an extent in a database system 10 according to anexemplary embodiment of the present disclosure may be implemented by thefollowing modules.

According to an exemplary embodiment of the present disclosure, thedatabase system 10 may include a module 701 for deciding movement of anextent stored in a first disk in a disk space in which the disk spaceincludes at least two disks; a module 702 for determining, by theprocessor, whether there is writing work for the extent based on extentmapping information for the extent, a module 703 for changing, by theprocessor, a state of the extent to read-only in the extent mappinginformation when there is no writing work for the extent, a module 704for moving, by the processor, the extent positioned in the first disk toa second disk, and a module 705 for updating, by the processor, theextent mapping information based on completion of the disk movement ofthe extent.

FIG. 8 is a flow chart illustrating logic for moving an extent in adatabase system 10 according to an exemplary embodiment of the presentdisclosure.

The method for moving an extent in a database system 10 according to anexemplary embodiment of the present disclosure may be implemented by thefollowing logics.

According to an exemplary embodiment of the present disclosure, thedatabase system 10 may include a logic 801 for deciding movement of anextent stored in a first disk in a disk space in which the disk spaceincludes at least two disks; a logic 802 for determining, by theprocessor, whether there is writing work for the extent based on extentmapping information for the extent, a logic 803 for changing, by theprocessor, a state of the extent to read-only in the extent mappinginformation when there is no writing work for the extent, a logic 804for moving, by the processor, the extent positioned in the first disk toa second disk, and a logic 805 for updating, by the processor, theextent mapping information based on completion of the disk movement ofthe extent.

FIG. 9 is a flow chart illustrating a circuit for moving an extent in adatabase system 10 according to an exemplary embodiment of the presentdisclosure.

The method for moving an extent in a database system 10 according to anexemplary embodiment of the present disclosure may be implemented by thefollowing circuits.

According to an exemplary embodiment of the present disclosure, thedatabase system 10 may include a circuit 901 for deciding movement of anextent stored in a first disk in a disk space in which the disk spaceincludes at least two disks; a circuit 902 for determining, by theprocessor, whether there is writing work for the extent based on extentmapping information for the extent, a circuit 903 for changing, by theprocessor, a state of the extent to read-only in the extent mappinginformation when there is no writing work for the extent, a circuit 904for moving, by the processor, the extent positioned in the first disk toa second disk, and a circuit 905 for updating, by the processor, theextent mapping information based on completion of the disk movement ofthe extent.

Those skilled in the art needs to recognize that various illustrativelogical blocks, configurations, modules, circuits, means, logic, andalgorithm steps described in connection with the exemplary embodimentsdisclosed herein may be additionally implemented as electronic hardware,computer software, or combinations of both sides. To clearly illustratethe interchangeability of hardware and software, various illustrativecomponents, blocks, structures, means, logic, modules, circuits, andsteps have been described above generally in terms of theirfunctionalities. Whether the functionalities are implemented as thehardware or software depends on a specific application and designrestrictions given to an entire system. Skilled artisans may implementthe described functionalities in various ways for each particularapplication, but such implementation decisions should not be interpretedas causing a departure from the scope of the present disclosure.

FIG. 10 is a block diagram of a computing device according to anexemplary embodiment of the present disclosure.

FIG. 10 illustrates a simple and general schematic view of an exemplarycomputing environment in which the exemplary embodiments of the presentdisclosure may be implemented.

The present disclosure has generally been described above in associationwith a computer executable command which may be executed on one or morecomputers, but it will be well appreciated by those skilled in the artthat the present disclosure can be implemented through a combinationwith other program modules and/or a combination of hardware andsoftware.

In general, the program module includes a routine, a program, acomponent, a data structure, and the like that execute a specific taskor implement a specific abstract data type. Further, it will be wellappreciated by those skilled in the art that the method of the presentdisclosure can be implemented by other computer system configurationsincluding a personal computer, a handheld computing device,microprocessor-based or programmable home appliances, and others (therespective devices may operate in connection with one or more associateddevices as well as a single-processor or multi-processor computersystem, a mini computer, and a main frame computer.

The exemplary embodiments described in the present disclosure may alsobe implemented in a distributed computing environment in whichpredetermined tasks are performed by remote processing devices connectedthrough a communication network. In the distributed computingenvironment, the program module may be positioned in both local andremote memory storage devices.

The computer generally includes various computer readable media. Mediaaccessible by the computer may be computer readable media regardless oftypes thereof and the computer readable media include volatile andnon-volatile media, transitory and non-transitory media, and mobile andnon-mobile media. As not a limit but an example, the computer readablemedia may include both computer readable storage media and computerreadable transmission media. The computer readable storage media includevolatile and non-volatile media, temporary or non-temporary media, andmovable and non-movable media implemented by a predetermined method ortechnology for storing information such as a computer readable command,a data structure, a program module, or other data. The computer storagemedia include a RAM, a ROM, an EEPROM, a flash memory or other memorytechnologies, a CD-ROM, a digital video disk (DVD) or other optical diskstorage devices, a magnetic cassette, a magnetic tape, a magnetic diskstorage device or other magnetic storage devices or predetermined othermedia which may be accessed by the computer or may be used to storedesired information, but are not limited thereto.

The computer readable transmission media generally implement thecomputer readable command, the data structure, the program module, orother data in a carrier wave or a modulated data signal such as othertransport mechanism and include all information transfer media. The term“modulated data signal” means a signal acquired by configuring orchanging at least one of characteristics of the signal so as to encodeinformation in the signal. As an example rather than a limit, thecomputer readable transmission media include wired media such as a wirednetwork or a direct-wired connection and wireless media such asacoustic, RF, infrared and other wireless media. A combination of anymedia among the aforementioned media is also included in a range of thecomputer readable transmission media.

An exemplary environment 1100 that implements various aspects of thepresent disclosure including a computer 1102 is shown and the computer1102 includes a processing device 1104, a system memory 1106, and asystem bus 1108. The system bus 1108 connects system componentsincluding the system memory 1106 (not limited thereto) to the processingdevice 1104. The processing device 1104 may be a predetermined processoramong various commercial processors. A dual processor or othermulti-processor architectures may also be used as the processing device1104.

The system bus 1108 may be any one of several types of bus structureswhich may be additionally interconnected to a local bus using any one ofa memory bus, a peripheral device bus, and various commercial busarchitectures. The system memory 1106 includes a read only memory (ROM)1110 and a random access memory (RAM) 1112. A basic input/output system(BIOS) is stored in the non-volatile memories 1110 including the ROM,the EPROM, the EEPROM, and the like and the BIOS includes a basicroutine that assists in transmitting information among components in thecomputer 1102 at a time such as in-starting. The RAM 1112 may alsoinclude a high-speed RAM including a static RAM for caching data, andthe like.

The computer 1102 also includes an interior hard disk drive (HDD) 1114(for example, EIDE and SATA), in which the interior hard disk drive 1114may also be configured for an exterior purpose in an appropriate chassis(not illustrated), a magnetic floppy disk drive (FDD) 1116 (for example,for reading from or writing in a mobile diskette 1118), and an opticaldisk drive 1120 (for example, for reading a CD-ROM disk 1122 or readingfrom or writing in other high-capacity optical media such as the DVD,and the like). The hard disk drive 1114, the magnetic disk drive 1116,and the optical disk drive 1120 may be connected to the system bus 1108by a hard disk drive interface 1124, a magnetic disk drive interface1126, and an optical drive interface 1128, respectively. An interface1124 for implementing an exterior drive includes at least one of auniversal serial bus (USB) and an IEEE 1394 interface technology or bothof them.

The drives and the computer readable media associated therewith providenon-volatile storage of the data, the data structure, the computerexecutable command, and others. In the case of the computer 1102, thedrives and the media correspond to storing of predetermined data in anappropriate digital format. In the description of the computer readablemedia, the mobile optical media such as the HDD, the mobile magneticdisk, and the CD or the DVD are mentioned, but it will be wellappreciated by those skilled in the art that other types of mediareadable by the computer such as a zip drive, a magnetic cassette, aflash memory card, a cartridge, and others may also be used in anexemplary operating environment and further, the predetermined media mayinclude computer executable commands for executing the methods of thepresent disclosure.

Multiple program modules including an operating system 1130, one or moreapplication programs 1132, other program module 1134, and program data1136 may be stored in the drive and the RAM 1112. All or some of theoperating system, the application, the module, and/or the data may alsobe cached by the RAM 1112. It will be well appreciated that the presentdisclosure may be implemented in various operating systems which arecommercially usable or a combination of the operating systems.

A user may input commands and information in the computer 1102 throughone or more wired/wireless input devices, for example, pointing devicessuch as a keyboard 1138 and a mouse 1140. Other input devices (notillustrated) may include a microphone, an IR remote controller, ajoystick, a game pad, a stylus pen, a touch screen, and others. Theseand other input devices are often connected to the processing device1104 through an input device interface 1142 connected to the system bus1108, but may be connected by other interfaces including a parallelport, an IEEE 1394 serial port, a game port, a USB port, an IRinterface, and others.

A monitor 1144 or other types of display devices are also connected tothe system bus 1108 through interfaces such as a video adapter 1146, andthe like. In addition to the monitor 1144, the computer generallyincludes a speaker, a printer, and other peripheral output devices (notillustrated).

The computer 1102 may operate in a networked environment by using alogical connection to one or more remote computers including remotecomputer(s) 1148 through wired and/or wireless communication. The remotecomputer(s) 1148 may be a workstation, a computer device computer, arouter, a personal computer, a portable computer, a micro-processorbased entertainment apparatus, a peer device, or other general networknodes and generally includes multiple components or all of thecomponents described with respect to the computer 1102, but only amemory storage device 1150 is illustrated for brief description. Theillustrated logical connection includes a wired/wireless connection to alocal area network (LAN) 1152 and/or a larger network, for example, awide area network (WAN) 1154. The LAN and WAN networking environmentsare general environments in offices and companies and facilitate anenterprise-wide computer network such as Intranet, and all of them maybe connected to a worldwide computer network, for example, the Internet.

When the computer 1102 is used in the LAN networking environment, thecomputer 1102 is connected to a local network 1152 through a wiredand/or wireless communication network interface or an adapter 1156. Theadapter 1156 may facilitate the wired or wireless communication to theLAN 1152 and the LAN 1152 also includes a wireless access pointinstalled therein in order to communicate with the wireless adapter1156. When the computer 1102 is used in the WAN networking environment,the computer 1102 may include a modem 1158 or has other means thatconfigure communication through the WAN 1154 such as connection to acommunication computing device on the WAN 1154 or connection through theInternet. The modem 1158 which may be an internal or external and wiredor wireless device is connected to the system bus 1108 through theserial port interface 1142. In the networked environment, the programmodules described with respect to the computer 1102 or some thereof maybe stored in the remote memory/storage device 1150. It will be wellknown that illustrated network connection is exemplary and other meansconfiguring a communication link among computers may be used.

The computer 1102 performs an operation of communicating withpredetermined wireless devices or entities which are disposed andoperated by the wireless communication, for example, the printer, ascanner, a desktop and/or a portable computer, a portable data assistant(PDA), a communication satellite, predetermined equipment or placeassociated with a wireless detectable tag, and a telephone. This atleast includes wireless fidelity (Wi-Fi) and a Bluetooth wirelesstechnology. Accordingly, communication may be a predefined structurelike the network in the related art or just ad hoc communication betweenat least two devices.

The Wi-Fi enables connection to the Internet, and the like without awired cable. The Wi-Fi is a wireless technology such as a device, forexample, a cellular phone which enables the computer to transmit andreceive data indoors or outdoors, that is, anywhere in a communicationrange of a base station. The Wi-Fi network uses a wireless technologycalled IEEE 802.11(a, b, g, and others) in order to provide safe,reliable, and high-speed wireless connection. The Wi-Fi may be used toconnect the computers to each other or the Internet and the wirednetwork (using IEEE 802.3 or Ethernet). The Wi-Fi network may operate,for example, at a data rate of 11 Mbps (802.11a) or 54 Mbps (802.11b) inunlicensed 2.4 and 5 GHz wireless bands or operate in a productincluding both bands (dual bands).

It will be appreciated by those skilled in the art that information andsignals may be expressed by using various different predeterminedtechnologies and techniques. For example, data, instructions, commands,information, signals, bits, symbols, and chips which may be referred inthe above description may be expressed by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or predetermined combinations thereof.

It may be appreciated by those skilled in the art that various exemplarylogical blocks, modules, processors, means, circuits, and algorithmsteps described in association with the embodiments disclosed herein maybe implemented by electronic hardware, various types of programs ordesign codes (for easy description, herein, designated as “software”),or a combination of all of them. In order to clearly describe theintercompatibility of the hardware and the software, various exemplarycomponents, blocks, modules, circuits, and steps have been generallydescribed above in association with functions thereof. Whether thefunctions are implemented as the hardware or software depends on designrestrictions given to a specific application and an entire system. Thoseskilled in the art of the present disclosure may implement functionsdescribed by various methods with respect to each specific application,but it should not be analyzed that the implementation determinationdeparts from the scope of the present disclosure.

Further, various embodiments presented herein may be implemented asmanufactured articles using a method, an apparatus, or a standardprogramming and/or engineering technique. The term “manufacturedarticle” includes a computer program, a carrier, or a medium which isaccessible by a predetermined computer-readable device. Herein, themedia may include storage media and transmission media. For example, acomputer-readable storage medium includes a magnetic storage device (forexample, a hard disk, a floppy disk, a magnetic strip, or the like), anoptical disk (for example, a CD, a DVD, or the like), a smart card, anda flash memory device (for example, an EEPROM, a card, a stick, a keydrive, or the like), but is not limited thereto. Further, variousstorage media presented herein include one or more devices and/or othermachine-readable media for storing information. Further the transmissionmedia include a wireless channel and various other media which arecapable of transferring a command(s) and/or data, but are not limitedthereto.

It will be appreciated that a specific order or a hierarchical structureof steps in the presented processes is one example of exemplaryaccesses. It will be appreciated that the specific order or thehierarchical structure of the steps in the processes within the scope ofthe present disclosure may be rearranged based on design priorities.Appended method claims provide elements of various steps in a sampleorder, but it does not mean that the method claims are limited to thepresented specific order or hierarchical structure.

The description of the presented embodiments is provided so that thoseskilled in the art of the present disclosure use or implement thepresent disclosure. Various modifications of the embodiments will beapparent to those skilled in the art and general principles definedherein can be applied to other embodiments without departing from thescope of the present disclosure. Therefore, the present disclosure isnot limited to the embodiments presented herein, but should be analyzedwithin the widest range which is consistent with the principles and newfeatures presented herein.

What is claimed is:
 1. A computer program stored in a computer-readablestorage medium, wherein the computer program executes a method formoving an extent when the computer program is executed by one or moreprocessors of a computing device, the method comprising: deciding, bythe one or more processors, movement of an extent stored in a first diskin a disk space in which the disk space includes at least two disks;determining, by the one or more processors, that there is a writing workfor the extent when there is a transaction sequence number of a workerthread less than or equal to a transaction sequence number of the extentmapping information by comparing the transaction sequence number of theextent mapping information and the transaction sequence number of theworker thread; switching, by the one or more processors, the workerthread performing the writing work for the extent to a sleep state whenthere is the writing work for the extent; changing, by the one or moreprocessors, a state of the extent to read-only in the extent mappinginformation when there is no writing work for the extent; moving, by theone or more processors, the extent positioned in the first disk to asecond disk; and updating, by the one or more processors, the extentmapping information based on completion of the movement of the extent.2. The computer program stored in the computer-readable storage mediumof claim 1, wherein the extent mapping information is configured foreach extent and includes at least one information of address informationof the extent, state information of the extent, and a transactionsequence number of the extent.
 3. The computer program stored in thecomputer-readable storage medium of claim 2, wherein when the writingwork for the extent occurs, the transaction sequence number is updatedto the transaction sequence number of a worker thread performing thewriting work for the extent.
 4. The computer program stored in thecomputer-readable storage medium of claim 1, wherein the method furtherincludes modifying, when the writing work for the extent is completed,the transaction sequence number of the extent mapping information to thetransaction sequence number of the worker thread.
 5. The computerprogram stored in the computer-readable storage medium of claim 1,wherein the updating, by the one or more processors, the extent mappinginformation based on completion of the movement of the extent includes:determining, by the one or more processors, whether there is the writingwork for the extent when the movement of the extent is completed, andchanging an extent state of the extent mapping information to loadingwhen there is the writing work for the extent, updating the extentmapping information by waiting for the completion of the writing work,or updating the extent mapping information when there is the no writingwork for the extent.
 6. The computer program stored in thecomputer-readable storage medium of claim 5, wherein when the extentstate of the extent mapping information is loading, a worker threadaccessing the extent mapping information is switched to a standby stateand written in a standby list.
 7. The computer program stored in thecomputer-readable storage medium of claim 1, wherein the movement forthe extent stored in the first disk is decided for rebalancing when anew disk is added to the disk space, one or more disks are removed, oran error occurs in one of the at least two disks.
 8. The computerprogram stored in the computer-readable storage medium of claim 1,wherein the method further includes resuming, by the one or moreprocessors, the writing work for the extent based on the update of theextent mapping information.
 9. The computer program stored in thecomputer-readable storage medium of claim 1, wherein the method furtherincludes deleting, by the one or more processors, the extent positionedin the first disk.
 10. A method for moving an extent, which is performedby one or more processors of a computing device, the method comprising:deciding, by the one or more processors, movement of an extent stored ina first disk in a disk space in which the disk space includes at leasttwo disks; determining, by the one or more processors, that there is awriting work for the extent when there is a transaction sequence numberof a worker thread less than or equal to a transaction sequence numberof the extent mapping information by comparing the transaction sequencenumber of the extent mapping information and the transaction sequencenumber of the worker thread; switching, by the one or more processors,the worker thread performing the writing work for the extent to a sleepstate when there is the writing work for the extent; changing, by theone or more processors, a state of the extent to read-only in the extentmapping information when there is no writing work for the extent;moving, by the one or more processors, the extent positioned in thefirst disk to a second disk; and updating, by the one or moreprocessors, the extent mapping information based on completion of themovement of the extent.
 11. A computing device comprising: one or moreprocessors; and memory storing commands executable in the one or moreprocessors, wherein the one or more processors is configured to: decidemovement of an extent stored in a first disk in a disk space in whichthe disk space includes at least two disks, determine that there is awriting work for the extent when there is a transaction sequence numberof a worker thread less than or equal to a transaction sequence numberof the extent mapping information by comparing the transaction sequencenumber of the extent mapping information and the transaction sequencenumber of the worker thread, switch the worker thread performing thewriting work for the extent to a sleep state when there is the writingwork for the extent, change a state of the extent to read-only in theextent mapping information when there is no writing work for the extent,move the extent positioned in the first disk to a second disk, andupdate the extent mapping information based on completion of themovement of the extent.